We have characterized the pattern of proto-oncogene and growth factor mRNA expression in a battery of human colorectal carcinoma and glioma cell lines. With regard to the glioma cell lines, analysis of mRNA expression of 6 proto-oncogenes revealed marked heterogeneity of expression between cell lines only for the sis proto-oncogene, which encodes for a protein having marked homology to the B chain of platelet-derived growth factor. The presence of detectable mRNA in these lines correlated in addition with the presence of a pleomorphicglial cell morphologic heterogeneity among glioblastoma cell lines may represent various points of arrest along a developmental pathway of the human astrocyte, with the presence of detectable levels of sis and GFAP MRNA correlating with a more differentiated phenotype. We have tested a battery of these glioma lines with varying morphology with suramin. Our preliminary data shows that the presence of sis MRNA in a cell line serves as a marker for increased suramin sensitivity. In addition, the degree of sis mRNA signal intensity is also proportional to that cell line's LD50 to suramin. No significant variations in cell line morphology have been observed. With regard to suramin sensitivity in human prostate and colorectal cell lines, there appears to be significant variation. In addition, with regard to prostate lines, suramin's growth inhibitory effect appears to be mediated via mechanisms which are not entirely androgen independent.